Biological materials, such as proteins, peptides, nucleic acids, bacteria, cells, antibodies, enzymes, serums, vaccines, liposomes, and viruses, are generally unstable when stored in media or other liquid solutions. For example, enveloped viruses such as live influenza virus manufactured from egg allantoid fluid loose one log of potency, defined as Tissue Culture Infectious Dose (TCID50), in less than two to three weeks when stored under refrigerated temperature, i.e. approximately 4° C. At room temperature conditions (approximately 25° C.) and at warmer temperatures such as 37° C., the virus looses the such potency in a matter of days to hours, respectively. Lyophilization processes, where aqueous formulas are frozen then dried by sublimation, are commonly used to stabilize these biological materials. Spray-drying is another process commonly used to remove water from biological materials for storage. Substitution of protectant molecules, such as carbohydrates, after removal of water can increase stability by preventing chemical degradation, denaturation, and growth of microbial contaminants.
In lyophilization (freeze-drying), the biological material is commonly mixed as a solution or suspension with protective agents, frozen, and dehydrated by sublimation and secondary drying. The low temperatures of freezing and drying by sublimation can slow the kinetics of degradation reactions but they can also reduce the ability of protective agents to penetrate certain biological materials. Moreover, the low temperatures and low surface to volume ratios involved in freeze drying can require long drying times.
Lyophilization and secondary drying processes can force a protein or cell, for example, to undergo significant chemical and physical changes. Such changes can result in loss of activity of the protein due to concentration of salts, precipitation/crystallization, shear stress, pH extremes, and residual moisture remaining through the freeze-drying. Freeze-drying can pierce cells with ice crystals and fail to protect internal compartments.
The formation of powder particles by grinding or lyophilized cakes or by spray drying is of substantial interest and importance to the biopharmaceutical industry for preservation of biologically active materials. Not only can such fine particles provide a convenient storage form for biomaterials such as proteins, non-protein biomolecules (including for example, DNA, RNA, lipids, and carbohydrates), but they can be substantially dehydrated for long-term storage and rewettable for administration of the biomaterial for its intended use after the storage period. Further, such dried fine particles could be produced in a controlled diameter range and may be administered as a dried aerosol power, for example, via the intranasal route, wherein the nasal mucosa would provide for rewetting and resolvation of the biomaterial in a patient. Numerous other uses of such fine and microfine particles containing a biomaterial would find use in the art of pharmaceutics, biologics, and particularly in the field of live virus vaccines. Thus, it would be advantageous to develop methods of forming fine particles containing biologically active materials.
Spray drying is a well known process long used, e.g., in the food processing industry to produce powders. For example, liquid products, such as milk, are sprayed through a nozzle into a stream of hot gasses to produce a powder. The increased surface area exposed in the spray mist, in combination with the high temperatures of the drying gas, provides rapid removal of water from the liquid product. However, such process conditions are often unsuitable for sensitive biologic materials due to the shear stress, heat stress, oxidative stress, and conformational changes that can occur with loss of hydration water at high temperatures. Some of these problems are addressed in pharmaceutical spray drying methods, such as those described in U.S. Pat. No. 5,902,844, Spray Drying of Pharmaceutical Formulations Containing Amino Acid-Based Materials, to Wilson. In Wilson, peptides in solution with a water soluble polymer are sprayed into a stream of drying gas to form a pharmaceutical composition. The presence of the polymer can protect the peptide from degradation by coating the peptide against chemical attacks and by substituting for water of hydration lost during drying. Certain sensitive peptides and other biological materials, such as nucleic acids, bacteria, cells, antibodies, enzymes, serums, vaccines, liposomes, and viruses can still be damaged, however, by the heat, shear stress and dehydration of the processes described by Wilson, and the like.
Larger and more complex biologics, such as live virus and bacterial vaccines, are well recognized as being among the most unstable products. For example, enveloped viruses such as live influenza virus manufactured from egg allantoid fluid loose one log of potency, defined as Tissue Culture Infectious Dose (TCID50), in less than two to three weeks when stored under refrigerated temperature, i.e. approximately 4° C. At room temperature conditions (approximately 25° C.), the virus looses the such potency in a matter of days.
A need remains for methods to preserve sensitive biological materials, such as proteins and live viruses in storage, particularly at temperatures above freezing. Methods to prepare dry powder particles using processes with quick low temperature drying are desirable to suit the sensitivities of particular biologic materials. What's more, spray drying processes that do not require exposure to organic co-solvents can reduce denaturation of sensitive biological structures. Compositions that can protect such biologicals in storage would provide benefits in medicine and scientific research. The present invention provides these and other features that will become apparent upon review of the following.